Combined rheostat and potentiometer



Patented Apr. 20, 1926.

UNITED STATES PATENT OFFICE.

CLAUDE F. CAIRNS, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOR TO ACME APPARATUS COMPANY, OF CAMBRIDGE, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.,

COMBINED RHEOSTAT AND POTENTIOMETER.

Application led August 2, 1922. Serial No. 579,130.

To aZZ whom, z't may concern:

Be it known that I, CLAUDE F. CAIRNs, of Cambridge, in the county of Middlesex and State of Massachusetts, a citizen of the United States, have invented a new and useful Improvement in Combined Rheostats and Potentiometers, of whichthe following is a specification.

In various classes of electrical work, more particularly in radio circuits, it is desirable to combine in one instrument a rheostat and potentiometer in such manner that, while the two may be separately adjusted or used, they will be arranged together in very small compass. My invention relates to such an arrangement, being not concerned with any improvement in the type of apparatus itself but rather in the combination of the two instrument-s so that they will be in the smallest possible compass and at the same time so that each will be capable of independent operation. It is therefore the object of my invention to provide a single instrument octhe smallest permissible amount of space whereby the variation of the rheostat resistance element will vary the intensity of the current in an external circuit and whereby, quite independently of such variation of current intensity, the diii'erence of potential between one terminal of the potentiometer resistance element and the means for dividing the resistance'of' said element may be varied by the actuation of such resistancedividing means.

With the foregoing object in view my invention in its broadest aspect comprises a potentiometer resistance element and a rheostat resistance element preferably mounted on an insulating'frame, said elements being ar ranged concentrically and one surrounding theother to economize space and for convenience of independentl operation, together with means such as a rotatable contact member for varying the resistance of the rheostat resistance element, and other means such as a rotatable contact member for dividing the resistance of the potentiometer resistance element. The means for actuating the potentiometer resistance dividing means and the rheostat resistance varying means comprises preferably a sleeve having its bearing in the insulating frame and a rod mounted in but insulated from said sleeve, together with knobs secured respectively to said sleeve and rod, one projecting beyond the other whereby said sleeve and rod and consequently their attached contact arms may be rotated each independently of the other.

Terminal members are provided for connecting the said resistance elements and the contact arms to external circuits, one terminal of the rheostat resistance element and the means for varying the same being arranged for connection to a circuit including a source of electromotive force, such as the.

ilament circuit of a vacuum tube, in which the current intensity is to be varied, and the terminals of the potentiometer resistance element are arranged to be connected across the terminals of the same or a 4dierent source of electromotive force, while the potentiometer resistance dividing means is arranged to be connected directly or indirectly to an element whose potential is to be varied, tszulch for instance as the grid of a vacuum My invention will be understood by reference to the drawings in which- Figure 1 is a rear view, uncovered, of a device embodying my invention;

Fig. 2 being a front view thereof, and

Fig. 3 a section on line 3- -3 of Fig. 1.

Fig. 4 is a diagram showing the connection of my improved combined rheostat and potentiometer to external circuits', the latter being indicated in dotted lines.

In the particular drawings selected for more fully disclosing my invention, 1 is a casing or :trame made of insulating material and mounted on a standard 2 to which it is connected by a nut and bolt 3. This casing is generally circular in shape and has a iiange 4: projecting from it having a substantially circular periphery. Around this flange is mounted -the potentiometer coil or resistance element which consists of a strip ot insulating material 5 on which is wound resistance wire 6, this construction being securely fastened to the casing. The ln'nd and size of wire may be determined according to the circumstances under which the apparatus is to be used. Each end of the wire -6 is connected in a suitable way with a terminal member 7 and 8 herein shown as binding screws from which run wires 9 and Within the flange is mounted the rheostat resistance element upon an insulating sup-y Aus a resist-ance wire 12 which is thus surround- The terminal member 13 is herein shown as a binding screw to which one end of the resistance wire 12 is attached, the other end of the resistance wire bein free or dead-ended. The core may be omitte if the Wire is strong enough.

Through the center of the casing is a tube 131 carrying at its front end a collar 14 attached thereto by a screw 15 and also carrying a pointer 16. To the collar 14 is attached a handle 17 of insulatingmaterial so that by turning the handle the pointer and tube will be turned.

' The' tube 131 passes through. a bearlng 19 located in a suitable opening inthe ca sing or frame 1 and preferably held therein by a nut 20. On t e further end ofl this bearing is attached a contact arm 21 which is held in place by means of a collar 22 and set screw 23. The contact arm 21 is electrically connected to the binding screw or terminal member 24 through the bearinor 19 and the metal strip 241, one end of which lies between the end of the bearing 19-and its nut 20 and a collar 201 attached to the tube 131 by a set screw. The other end is attached to a screw 240 which is electrically connected to the binding screw 24, this construction being such that the binding screw is connected through the contact arm 21 with the resistance coil 12.- Thus the amount of resistance thrown into the circuit will be controlled by turning the handle 17, thus turning the tube 131 and contact arm 21, the circuit being from binding screw 13, resistance coil 12, contact arm 21, bearing 19, tube 131 and strip 241 to the binding screw 24.

Within the tube 131 and the collar 14 is a sleeve 25 of insulating material having a flange at its rear within which sleeve is a suitable rod 26 having at its forward end a handle or knob 27 of insulating material. The further end of the rod 26 carries a contact arm 28 the end of which vrests upon the wire 6 of the potentiometer and divides the resistance thereof. 'This contact arm 28 is electrically connected by the metal strip 29 with a terminal member 30 herein shown asa binding screw. The contact arm 28 and strip 29 are attached to the rod 26 by a collar 261 and set screw 262.

On the front side of the device is a dial 31 held by screws 310 and nuts 311 about which dial a graduated scale may be marked as shown, to indicate the relative amount 'of resistance thrown in the circuit, the pointer 16 being properly adjusted for the purpose, the throwing in of the resistance being caused by the turning of the handle 27.

From the foregoing it will be understood that the rheostat resistance element vary- `16 carried by ing means or contact arm 21 is mechanically and electrically. connected to the tube 131, and may be adjusted over the rheostat resistance element by turning the handle 17 so as to throw any desired 'amount of resistance into the external circuit in which-said resistance element and arm are connected throughzthe terminal members 13, 24, which circuit may include a vacuum tube filament F, or any other conducting member, and also the battery A, as indicated in dotted lines in Fig. 4, the current passing through said arm and.' tube to the strip 241 and thence through the screw 240 to the terminal 24,

the battery A, filament F, terminal element- 13 and that portion of saidy resistance element 12 between said element 13 and said contact arm 21. The lresistance thus thrown in will beindicated on the graduated dial 31, if the latter be employed, by the pointer said dial.

the tube 131 and movable' over It; will be understood also that any desired amount of the resistance of the potentiometer resistance element 6 may be utilized by adjusting the arm 28 along said element by turning the handle or knob 27, said arm bein electrically connected to the .terminal mem er 30 through the collar 261 and strip 29 and the adjustment of said arm being entirely independent of the arm 21. The division of the resistance of the potentiometer,

resistance element 6 by the arm 28 is utilized for varying the diii'erence of potential between one of the terminal members 7, 8, connected to a source of electromotive force A' as indicated in dotted lines in Fig. 4, and said arm 28 or said terminal member 3Q te which said arm is connected, so that the potential of some element connected to said terminal member 30, such as the tube, may be varied.

While my invention may be otherwise grid of a vacuuir embodied, it utilizes two concentric shafts one of which controls the potentiometer and the other the rheostat, both being .arranged in such a Way that either potentiometer or rheostat may be separately adjusted and the adjustment of the resistance indicated. It

-willvbe noted that this apparatus as shown saves space, is easy and economical of manufacture and makes the control of vacuum tubes and other appropriate apparatus much easier and simpler than other arrangements of potentiometers'and rheostats now in use. It siiiiiciently long screws 310 are used the device may be attached to a panel.

Having thus described an illustrative embodiment of my invention without however limiting myself thereto, what I claim and desire to secure by Letters Patent is:

1. combined rheostat and potentiometer comprising 1n combination, an insulating frame having a circular flange ,projecting laterally therefrom, a potentiometer resis- :leerme tance element mount-ed on said frame on one side of said flange, a rheostat resistance element mounted on said lframe on the other side of said liange, said elements being arranged concentrically and one surrounding the other, terminal members connected respectively to the end of the potentiometer resistance element, a terminal member connected to one end of said rheostat resistance element, the other end thereof being tree or deadlended, a tubular sleeve rotatably mounted in said frameand projecting from either side thereof, a rheostat contact member mechanic-ally and electrically connected to said sleeve and having its tree end in cooperation with said rheostat resistance element, means for electrically connecting said tubular sleeve and the said terminal member connected t0 one end of said rheostat resistance element to a circuit containing a source of electromotive torce, whereby the current intensity in said circuit may be varied by the rotation of said tubular sleeve and the rheostat contact member connected thereto, a rod rotatably mounted in but insulated fromI said tubular sleeve, a potentiometer contact 'member mechanically and electrically connected to said rod and having its free end in cooperation with said potentiometer resistance element, a terminal member electrically connected to said rod, the said terminal members connected respectively to the ends of said potentiometer resistance element being arranged for connection to a source of electromotive force whereby the potential difference between one of said terminal members connected respectively to the ends of said potentiometer resistance element and the terminal member connected to said rod may be varied by the rotation of said rod and the potentiometer contact member connected thereto, and knobs secured to said tubular sleeve and rod, respectively, one projecting beyond the other, whereby said tubular sleeve and rod may be rotated each independently of the other.

2. A combined rheostat and potentiometer comprising in combination an insulating frame, a potentiometer resistance element and a rheostat resistance element mounted on said trame, said elements being arranged concentrically and one surrounding the other, means for dividing the resistance of said lpotentiometer resistance element, other means for varying the resistance ot said rheostat resistance element, each of said means being independent of the other, terminal members connected respectively t0 the ends of said potentiometer resistance element', a terminal member connected to the means for dividing the resistance of said potentiometer resistance element, the said terminal members connected respectively to the ends of said potentiometer resistance element being arranged for connection to a source of electromotive force whereby the potential difference between one of said terminal members connected respectively to the ends of said potentiometer resistance element and the. means for dividing the resistance of said potentiometer resistance element may be varied by said means for dividing the resistance of said potentiometer resistance element, a terminal member connected to one end of said rheostat resistance element, the other end thereof being tree or dead-ended, a terminal member connected to the means for varying the resistance of said rheostat resistance element` and means connecting the last mentioned means and the said terminal member connected to one end of said rheostat resistance element to a circuit containing a source of electromotive force, whereby the current intensity in said circuit may be varied by said means for varying the resistance of said rheostat resistance element.

3. A combined rheostat and potentiometer comprising in combination an insulating frame, a potentiometer resistance element and a rheostat resistance element mounted in said trame, said elements being arranged concentrically and one surrounding the other, means for dividing the resistance of said potentiometer resistance element, other means for varying the resistance off said rheostat resistance element, each said means being independent of the other, and' means for connecting each of said means and each of said resistance elements to externa-l circuits, whereby the division of said potentiometer resistance element will vary the di'erence of potential between the said means for dividing the resistance of said potentiometer resistance element and one of the terminals of said potentiometer resistancel element, an the variation ot' said rheostat resistance element will vary the intensity ot the current in the circuit in which said rheostat resistance element is included.

CLAUDE r. lcamas 

